This section introduces aspects that may be helpful to facilitating a better understanding of the invention. Accordingly, the statements of this section are to be read in this light. The statements of this section are not to be understood as admissions about what is in the prior art or what is not in the prior art.
Certain surfaces having a nanostructured or microstructured surface with raised features may provide a superhydrophobic surface. E.g., as discussed in U.S. Patent Applications 2005/0039661 and 2004/0191127, which are incorporated by reference herein in their entirety, a droplet of fluid on a superhydrophobic surface will appear as a suspended drop having a contact angle of at least about 140 degrees. Applying a voltage between the surface and the droplet can cause the surface to become electro-wetted, as indicated by the suspended drop having a contact angle of less than 90 degrees.
In many applications, it is desirable to be able to control the passage of a fluid below the surface and through a substrate supporting the nanostructures or microstructures. For example, as discussed in the 10/835,639 application, electro-wetting or changes in ambient pressure can be used to actuate a fluid to penetrate into structured surfaces located on a substrate and through openings in the substrate. In some cases, however, the fluid may go down to the bottom of the structured surfaces, but not pass through the openings.
Embodiments of the invention overcome this deficiency by providing an apparatus that facilitates the passage of fluid through the openings.